Semi-compliant medical balloon

ABSTRACT

A semi-compliant fiber-reinforced medical balloon having a folded wall thickness of from about 0.0010 to about 0.0060 inches and a rated burst pressure of at least 15 atmospheres and exhibiting compliance in the radial direction of from 0.5% expansion per atmosphere to about 1.0% expansion per atmosphere when pressurized from a fully inflated diameter to the rated burst pressure of the balloon includes a base balloon formed from a semi-elastic polymer material having an elongation to break of from about 10% to about 20%, a fiber layer is disposed over the base balloon with fibers having an elongation to break of from about 10% to about 20% and an outer layer formed from a semi-elastic polymer material having an elongation to break of from about 10% to about 20% disposed over the fiber layer.

TECHNICAL FIELD

This disclosure relates to medical dilation balloons; and, inparticular, it relates to semi-compliant medical balloons useful inangioplasty, stent placement and dilation and other medical applicationsincluding cardiology, radiology, urology and orthopedics.

BACKGROUND

Non-compliant medical balloons for performing angioplasty and othermedical procedures are known. U.S. Pat. No. 6,746,425 to Beckhamdiscloses a non-compliant medical balloon and methods for manufacturingthe balloon. U.S. Patent Application Publication No. US 2006/0085022 toHayes et al. discloses a non-compliant medical balloon having anintegral woven fabric layer and methods for manufacturing the balloon.U.S. Patent Application Publication No. US 2006/0085023 to Davies, Jr.et al. discloses a medical balloon having strengthening rods and methodsfor manufacturing the balloon. U.S. Patent Application Publication No.US 2006/0085024 to Pepper et al. discloses a non-compliant medicalballoon having an integral non-woven fabric layer and methods formanufacturing the balloon. U.S. Pat. No. 6,746,425 and Publication Nos.US 2006/0085022, US 2006/0085023 and US 2006/0085024 are herebyincorporated herein by reference.

Medical balloons are widely used in a variety of medical procedures.Typically, an uninflated medical balloon is inserted into a body-space,e.g., blood vessel, urological vessel, etc. by means of a catheter.After positioning at the desired location within the body, the medicalballoon may be inflated by introducing a pressurized fluid into theballoon through the catheter. The pressurized fluid causes the medicalballoon to expand, and the adjacent body-space is similarly expanded.The fluid may then be withdrawn from the balloon, causing it to collapseto facilitate its removal from the body. Medical balloons are also usedfor temporarily occluding vessels, placing medical devices such asstents, drug delivery and heat transfer.

Medical balloons are generally referred to as compliant, non-compliantand semi-compliant. Balloon compliance is a term used to describe thechange in a balloon's diameter as a function of pressure. Low pressurecompliant medical balloons are typically formed from elastomers such aslatex, polyurethane and other thermoplastic elastomers. Low pressurecompliant medical balloons may expand by 100% or greater upon inflation.Compliant medical balloons are typically used for fixation andocclusion.

Alternatively, high pressure non-compliant dilation balloons expand verylittle, if at all, when pressurized from a nominal diameter to a ratedburst pressure. The rated burst pressure is the maximum pressure atwhich there is a statistical 95% confidence level that 99.9% of thepopulation of balloons will not burst. High pressure non-compliantballoons may have rated burst pressures of up to 20 atmospheres orhigher. Generally, high pressure, non-compliant balloons are formed fromrelatively inelastic materials such as oriented highly crystallinepolyethylene terephthalate (PET) films. Such PET films provide hightensile strength, and may be used to form balloons with thin wallshaving high burst pressures. However, balloons formed from PET andsimilar materials having a high strength relative to wall thickness tendto be more susceptible to puncture. Balloons formed from PET also tendto be stiffer than balloons made from other more compliant materials.The stiffness of the deflated balloon directly affects its“trackability,” i.e., its ability to traverse sharp turns or branches ofthe vessels or body cavities through which the balloon must pass.Balloons having more flexible walls generally provide bettertrackability.

The term “semi-compliant” is used herein to describe a balloon thatexhibits a moderate degree of expansion when pressurized from itsoperating pressure (e.g. the pressure at which the balloon reaches itsnominal diameter) to its rated burst pressure. In some applications asemi-compliant balloon may be more desirable than a non-compliantballoon. Semi-compliant balloons tend to be less stiff thansemi-compliant balloons, resulting in better trackability.Semi-compliant balloons may also provide better puncture resistance thannon-compliant balloons. Thus, a practitioner may prefer a semi-compliantballoon over a non-compliant balloon in procedures where the balloonmust be used to expand a hard or calcified stenosis or where the balloonmust be threaded through small diameter blood vessels, and/or where theballoon has to traverse a torturous path. In some instances, asemi-compliant dilation balloon may be used to pre-dilate a stenosisbefore stent placement. A practitioner may also prefer a semi-compliantdilation balloon over a non-compliant balloon for stent placement and/orfor post-stent dilation.

Dilation balloons are often used to open or expand open body spacesrestricted by tough tissues such as strictures, scarring or calcifiedareas. In these applications medical dilation balloons having highoperating and burst pressures may be required. For example, dilationballoons are used in angioplasty, a procedure in which the balloon maybe used to expand a stenoic lesion. In these applications it isdesirable to make the outer wall of the dilation balloon as thin aspossible while still maintaining the required pressure rating or burststrength. It is also desirable that the balloon exhibit a high degree ofpuncture resistance.

In order to reduce the profile of the balloon, dilation balloons may beformed with pleated walls. When the balloon is deflated (i.e., before orafter inflation), these pleats are folded over, wrapped and/or rolledaround the long axis of the balloon. Consequently, the thinner the wallmaterial of the balloon, the smaller the diameter of theballoon-catheter assembly. A smaller diameter may be used with a smallerintroducer, reducing patient discomfort. A smaller diameter alsofacilitates passage of the deflated balloon through narrow vessels,lumens or cavities of the body prior to deployment.

Semi-compliant balloons may be produced from materials such as nylonwhich is softer than PET and provides moderate compliance and improvedtrackability. However, the tensile strength of nylons suitable forfabricating medical dilation balloons is typically less than that ofPET. Thus, a dilation balloon formed from a nylon or similarsemi-elastic material would require thicker walls in order to achievethe same burst pressures as PET dilation balloons. This in turnincreases the diameter of the balloon catheter assembly and the size ofthe introducer used in the procedure. Thus, there exists a need fordilation balloons having a moderate level of compliance, punctureresistance, high burst pressures and thin walls.

SUMMARY

In one aspect, a semi-compliant fiber-reinforced medical balloon thatmay be inflated and deflated, and when inflated exhibits a moderatechange in radial distension across a predetermined range of internalpressures includes a generally cylindrical barrel wall disposed betweentapered cone walls and cylindrical neck walls extending therefrom alonga longitudinal axis. The fiber-reinforced balloon may include a baseballoon formed from a semi-elastic polymer material having an elongationto break of from about 10% to about 20% and wherein the base balloondefines the cylindrical barrel wall, tapered cone walls and cylindricalneck walls. In one variation, a first fiber layer is disposed over thebase balloon with fibers having an elongation to break of from about 10%to about 20%. An outer layer formed from a semi-elastic polymer materialhaving an elongation to break of from about 10% to about 20% is disposedover the first fiber layer. The balloon has a rated burst pressure of atleast 15 atmospheres and exhibits compliance in the radial direction offrom 0.5% expansion per atmosphere to about 1.0% expansion peratmosphere when pressurized from a fully inflated diameter to the ratedburst pressure of the balloon. The balloon may be configured to have afolded wall thickness of from about 0.0010 to about 0.0060 inches.

The semi-compliant fiber-reinforced medical balloon may include aplurality of substantially semi-elastic fibers extending longitudinallyfrom one neck wall to the opposite neck wall along the longitudinal axisof the balloon with the fibers being substantially equally spaced apartaround the circumference of the balloon. In other variations, the firstfiber layer may be one of a woven, knitted, non-woven or braided fibermaterial. The fibers of the first fiber layer may have a thickness fromabout 0.0005 to about 0.025 inch and width-to-thickness ratio in therange from about 25:1 to about 45:1.

In another embodiment, the semi-compliant fiber-reinforced medicalballoon may include a second fiber layer disposed over the first fiberlayer. The fibers of the second fiber layer may be semi-elastic hoopfibers wrapped circumferentially around the balloon from one neck orcone wall to the opposite neck or cone wall such that the hoop fibersare substantially transverse to the longitudinal axis of the balloon. Inother variations, the second fiber layer may be one of a woven, knitted,non-woven or braided fiber material.

In another aspect, a fiber-reinforced medical balloon that may beinflated and deflated, includes a generally cylindrical barrel walldisposed between tapered cone walls and cylindrical neck walls extendingfrom the cone walls along the longitudinal axis of the balloon. Theballoon may include first and second fiber layers, the fibers of thefirst fiber layer being substantially inelastic and defining thecylindrical barrel wall, tapered cone walls and cylindrical neck walls.In this regard, the fibers of the first fiber layer may extendlongitudinally from one cone wall to the opposite cone wall along thelongitudinal axis of the balloon with the fibers being substantiallyequally spaced apart around the circumference of the balloon. A secondfiber layer may be disposed over the first fiber layer. In onevariation, the fibers of the second fiber layer are semi-elastic andhave an elongation to break of from about 10% to about 20%. An outerlayer formed from a semi-elastic polymer material having an elongationto break of from about 10% to about 20% may be disposed over the secondfiber layer. In one embodiment, the balloon has a rated burst pressureof at least 15 atmospheres and exhibits a compliance of from 0.5%expansion per atmosphere to about 1.0% expansion per atmosphere in aradial direction when pressurized from a fully inflated diameter to therated burst pressure of the balloon.

In different variations, the second fiber layer may be semi-elastic hoopfibers wrapped circumferentially around the balloon from one cone orneck wall to the opposite cone or neck wall such that hoop fibers aresubstantially transverse to the longitudinal axis of the balloon. Thehoop fibers may have a thickness from about 0.0005 to about 0.025 inchand width-to-thickness ratio in the range from about 25:1 to about 45:1.In yet other embodiments, the second fiber layer may be one of a woven,knitted, non-woven or braided fiber material.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding, reference is now made to thefollowing description taken in conjunction with the accompanyingDrawings in which:

FIG. 1A is a perspective view of a semi-compliant balloon according tothe disclosure:

FIG. 1B is a perspective view of the balloon of FIG. 1A in a foldedconfiguration;

FIG. 2 is a partial cut-away view of the balloon of FIG. 1A;

FIG. 3 illustrates a partial longitudinal cross-section through thebarrel wall of the balloon of FIG. 1A;

FIG. 4A is a side view of a tubular mandrel for constructing a balloonaccording to the disclosure;

FIG. 4B is a partial sectional view of the tubular mandrel 4A wherein atube of moldable material has been placed over the mandrel;

FIG. 5A is a side view of a preformed mandrel for constructing a balloonaccording to the disclosure;

FIG. 5B is a partial sectional view of the preformed mandrel of 5Awherein a moldable material has been placed over the mandrel;

FIG. 6 illustrates the placement of a first fiber layer includinglongitudinally extending fibers over a base balloon;

FIG. 7 illustrates the placement of circumferential or hoop extendingfibers over a base balloon and first fiber layer to form a second fiberlayer;

FIG. 8 illustrates one method of forming an outer layer over the firstand second fiber layers illustrated in FIGS. 6 and 7;

FIG. 9 illustrates an alternative method of forming a fiber layer;

FIG. 10 illustrates a woven fiber material for forming a fiber layer;

FIG. 11 illustrates a braided fiber material for forming a fiber layer;

FIG. 12 illustrates a knitted fiber material for forming a fiber layer;

FIG. 13 illustrates a non-woven fiber material for forming a fiberlayer;

FIG. 14 is a graph illustrating the compliance of various medicalballoons;

FIGS. 15, 15A and 15B illustrate the placement of fibers in a firstalternate construction of a semi-compliant balloon, FIG. 15 being a sideview of the balloon, FIG. 15A being an enlarged view of a section of theballoon when initially inflated, and FIG. 15B being an enlarged view ofthe same sections of the balloon when fully inflated;

FIG. 16 illustrates the placement of fibers in a second alternateconstruction of a semi-compliant balloon; and

FIG. 17 illustrates the placement of fibers in a third alternateconstruction of a semi-compliant balloon.

DETAILED DESCRIPTION

Referring now to the drawings, wherein like reference numbers are usedherein to designate like elements throughout, the various views andembodiments of semi-compliant medical balloons are illustrated anddescribed, and other possible embodiments are described. The Figures arenot necessarily drawn to scale, and in some instances the drawings havebeen exaggerated and/or simplified in places for illustrative purposesonly. One of ordinary skill in the art will appreciate the many possibleapplications and variations based on the following examples of possibleembodiments.

FIG. 1A is a side view of a fiber-reinforced semi-compliant medicaldilation balloon according to one embodiment. As illustrated, medicalballoon 100 is shown in a fully inflated state. Balloon 100 includes agenerally cylindrical barrel portion 102 disposed between tapered coneportions 104 and cylindrical neck portions 106 extending from the coneportions along a longitudinal axis 108 of the balloon. The outer surface110 of the cone portion 104 forms an angle 112 (the “cone angle”) withrespect to a longitudinal extension of the wall of the barrel portion102. Higher cone angles generally provide a shorter total balloonlength. In some embodiments, balloon 100 may have a cone angle 112 inthe range of 12 degrees to 22 degrees, in others from 18 degrees to 22degrees. In some embodiments, the cone angle 112 is about 20 degrees.

Referring to FIG. 1B, balloon 100 is illustrated in a deflated state Inits deflated state, the walls of barrel portion 102 and cone sections104 of balloon 100 form pleats or folds 120 with creases 122 between thefolds. As illustrated, folds 120 extend longitudinally from one neckportion 106 to the opposing neck portion 106. The pleated constructionof the cone and barrel sections, 104, 106 reduces the diameter ofballoon 100 to facilitate insertion of the balloon in its deflatedstate. Once positioned at the desired location, balloon 100 may beinflated through a catheter with a pressurized fluid such as a salinesolution. As balloon 100 is inflated, folds and creases 120, 122substantially disappear as the balloon reaches a fully inflated sizehaving a nominal diameter D1 as illustrated in FIG. 1A.

Since balloon 100 is semi-compliant, further increases in the pressureof the fluid used to inflate the balloon (i.e., beyond the pressureneeded to reach the nominal diameter D1) result in moderate furtherexpansion (indicated by the broken line in FIG. 1A) to diameter D2. Inone embodiment, semi-compliant balloon 100 expands at a rate of between0.5% per atmosphere to about 1.0% per atmosphere over a terminal portionof its expansion range (e.g., expansion beyond its fully inflateddiameter to its rated burst pressure). While balloon 100 may beconstructed to any dimensions, balloons having a deflated diameter inthe range from about 4 French Units (i.e., about 0.053 inches or 1.35millimeters) to about 12 French Units (i.e., about 0.158 inches or 4.0millimeters) are useful in the fields of cardiology, radiology,orthopedics and urology. In one embodiment, balloon 100 has a deflateddiameter in the range of 4 to 12 French Units and a folded (e.g. whenthe balloon is deflated) wall thickness of from about 0.0010 to about0.0060 inches.

FIG. 2 is a partial-sectional view of balloon 100, further illustratingthe structure of the balloon. In one embodiment, balloon 100 includes abase layer or base balloon 130. Base balloon 130 is formed from asuitable semi-elastic polymer such as a nylon or a polyether block amide(PEBA) such as PEBAX® brand PEBA having a Shore D hardness from about 25to about Shore D 54. In one embodiment, base balloon 130 has a doublewall thickness of from about 0.0012 inches to about 0.0016 inches.Positioned over base balloon 130 is a first fiber layer 132 including aplurality of semi-elastic longitudinally extending fibers 134. As usedherein, the term semi-elastic means a polymer material having anelongation to break of from about 10% to about 20%.

In one variation, fibers 134 are substantially the same length andextend from a first end 136 to a second end 138 of balloon 100. In otherembodiments, fibers 134 may have different lengths. For example, onegroup of longitudinal fibers 134 may extend over the entire length ofballoon 100 while another group of fibers may extend only over thelength of barrel 102 or over the length of the barrel and partially overthe cone. Longitudinally-oriented reinforcing fibers 134 may be orientedparallel or substantially parallel to one another and perpendicularwithin about 10 to 15 degrees to the balloon's longitudinal axis 108.

In one embodiment, fibers 134 may be attached to base balloon 130 with asuitable adhesive such as a polyurethane, a soluble, weldable polyamidematerial and/or embedded in a polymeric matrix. Fibers 134 may beselected from a semi-elastic material having an elongation to break offrom about 10% to about 20% such as a high tenacity polyester orpolyamide. Fibers 134 may have an elongation to break of from about 10%to about 20% to permit balloon 100 to expand moderately after reaching anominal diameter.

In one embodiment, a second fiber layer 140 is positioned over firstfiber layer 132. In one embodiment, second fiber layer 140 includes oneor more semi-elastic hoop or circumferential reinforcing fibers 142. Inone variation, one continuous hoop fiber 142 is wound over first fiberlayer 132 from first end 136 to second end 138 of balloon 100.Circumferential reinforcing fibers 142 may be parallel or substantiallyparallel to one another and perpendicular within about 15 degrees to thelongitudinally-oriented reinforcing fibers 134. In other embodiments,the second fiber layer may comprise a woven, non-woven, knitted orbraided fiber material wherein the fibers are semi-elastic.

Fiber or fibers 142 may be secured in position with suitable adhesivesuch as a polyurethane, and/or embedded in a polymeric matrix. In oneembodiment, fiber or fibers 142 are selected from a material having amoderate degree of compliance such as a high tenacity polyester or ahigh tenacity polyamide. In one variation fibers 134 are semi-elastic,e.g., selected to have an elongation to break of from about 10% to about20% to permit balloon 100 to expand moderately after reaching a fullyinflated state. In other embodiments, first and/or second fiber layers132, 140 may be formed from a woven, braided, knitted or non-wovenmaterial as hereinafter described.

In the illustrated embodiment, balloon 100 includes an outer layer 144.Outer layer 144 may provide additional material to increase thepuncture-resistance and surface smoothness of the balloon 100. Outerlayer 144 may be formed from the same material as base balloon 130 or adifferent material. Outer layer 144 may be formed from a suitablepolymer such as nylon or a polyether block amide such as PEBAX® brandPEBA. In one embodiment, base balloon 130 and outer layer 144 are formedfrom thermally-weldable polymer materials.

In one embodiment, to provide for moderate expansion beyond the fullyinflated state, the materials from which base balloon 130, first fiberlayer 132, second fiber layer 142 and outer layer 144 are selected to bephysically compatible. For example, if base balloon 130 is too soft,(e.g. too elastic, low tensile strength) relative to the material offibers 134 and 142, the base balloon may extrude and/or blow out betweenfibers 134 and 142 at less than the desired operating pressure.Alternatively, if the material of base balloon 130 is too hard (e.g. tooinelastic, high tensile strength), the base balloon may fail prematurelyand/or not provide the desired trackability and puncture resistance.Thus, the tensile properties (elasticity, tensile strength andelongation to break) of the materials used to form base balloon 130,longitudinal fibers 134 and hoop fibers 142 may be matched to preventfailure of the balloon while providing a high burst pressure andsemi-compliance. Likewise, outer layer 144 should have suitable tensileproperties (elasticity, tensile strength and elongation to break)sufficient to permit balloon 100 to expand moderately.

In other variations, it may be desirable to use substantially inelasticfibers for one of longitudinal fibers 134 and hoop fibers 142 toconstrain expansion of balloon 100 in either a radial or longitudinaldirection. For example, if longitudinal fibers 134 are formed from aninelastic or substantially inelastic material while hoop fibers 142 aremade from a semi-elastic material, balloon 100 may expand moderately ina radial direction while linear expansion of the balloon would beconstrained. Alternatively, if longitudinal fibers 134 are formed from asemi-elastic material with hoop fibers 142 formed from a substantiallyinelastic material, balloon 100 may expand in a longitudinal directionwith expansion in a radial direction being constrained by the hoopfibers.

Thus, in one embodiment, the use of a combination of semi-elastic andsubstantially inelastic fibers may provide a balloon that issemi-compliant in a first direction and non-compliant in a seconddirection. In the case where one of longitudinal fibers 134 and hoopfibers 142 is semi-elastic with the other being substantially inelastic,balloon 100 may be non-compliant in a first direction (longitudinally orradially) and semi-compliant in a second direction perpendicular orsubstantially perpendicular to the first direction.

In the embodiments of balloon 100 wherein a combination of semi-elasticand substantially inelastic reinforcing fibers are used, the inelasticfibers may be Kevlar, Vectran, Spectra, Dacron, Dyneema, Turlon (PBT),Zylon (PBO), polyimide (PIM) and ultrahigh molecular weightpolyethylenes In one variation, the inelastic reinforcing fiber may be amulti-filament Technora® brandparaphenylene/3,4-oxydiphenylene/terephthalamide copolymer.

FIG. 3 is a partial longitudinal section of wall 118 of balloon 100further illustrating construction of balloon 100. As illustratedlongitudinal fibers 134 and hoop fibers 142 are ribbon shaped to reducethe thickness of wall 118 while maintaining the cross-sectional area ofthe fibers. In different embodiments, fibers 134, 142 may have awidth-to-thickness ratio in the range from about 25:1 to about 45:1; inother variations the fibers may have a width-to-thickness ratio in therange from about 30:1 to about 40:1. In one embodiment, longitudinallyoriented fibers 134 of the first fiber layer 140, have a fiber densitygenerally about 15 to 30 fibers/inch having a fiber thickness of about0.0005 to 0.025 inch and placed equidistant from one another willprovide adequate strength in a longitudinal direction for astandard-sized semi-compliant medical balloon.

Fibers for use in balloon 100 may be supplied in the form of a bundle or“tow” of individual filaments. The tow typically has a generallycircular cross-section and may include an adhesive to hold the filamentstogether and retain the cross-sectional shape of the tow. Before use inconstructing balloon 100, the fiber tow may be drawn between one or morepair of closely spaced rolls to flatten the tow. A solvent orsolvent-based adhesive may be applied to the tow before it is drawnbetween the roll to soften any adhesive and facilitate rearrangement ofthe filaments within the tow. After flattening, the fiber may be dried,if necessary, and used or stored for later use. The process offlattening the fibers is described in greater detail in co-pending U.S.application Ser. No. 12/187,259, filed Aug. 6, 2008 for a “Non-CompliantMedical Balloon,” the disclosure of which is incorporated herein byreference for all purposes.

Turning to FIGS. 4A and 4B, in one embodiment, a removable tubularmandrel 400 may be used to assemble balloon 100. If balloon 100 isformed by stretch blow molding, mandrel 400 may be a tube of moldablematerial, such as a PET. A layer of moldable semi-elastic material 402of moldable polymer such as nylon 6, nylon 6.6 Nylon 11 or Nylon 12 isplaced over mandrel 400. Material 402 may be in the form of a tube asillustrated or as a film or tape wrapped around the mandrel. In otherembodiments, material 402 may be applied in the form of a solutionincluding the polymer that is applied to the mandrel by brushing,spraying or dipping. The tubular mandrel and the moldable material 402may be stretch blow molded to the shape of the desired finished balloon,such as balloon 100 of FIG. 1.

Turning to FIGS. 5A and 5B in another embodiment, a mandrel 500 may be apreform having the shape of the desired finished balloon as illustratedin FIG. 1A, in which case the mandrel may be a molded PET, a collapsiblemetal or polymeric foam, or formed from a wax or other low melting pointmaterial, or a material that may be removed by means of a solvent insubsequent processing. A layer of moldable semi-elastic material 502 ofmoldable polymer such as a poly-ether block amide, nylon 6, nylon 6.6Nylon 11 or Nylon 12 is placed over mandrel 500. Material 502 may be inthe form of a tube placed over the mandrel or film or tape wrappedaround mandrel 500. In some variations, material 502 may be a polymersolution applied to mandrel 500 that is applied to the mandrel bybrushing, spraying or dipping. In this variation, multiple layers of thesolution may be applied to mandrel 502 to achieve the desired thickness,with or without heating and/or curing between applications of thesolution.

FIG. 6 illustrates the placement of a first fiber layer 132 over baseballoon 130. As illustrated, in one embodiment, after base balloon 130is formed, a plurality of longitudinally oriented fibers 134 may be thenbe positioned on base balloon 130 to form first fiber layer 132.Longitudinally oriented fibers 134 may be applied to the base balloon byhand or mechanically. Mandrel 400 or 500 may be pressurized during theprocess to retain the desired shape as fibers 134 are applied over thebase balloon. In one embodiment, an adhesive such as a urethane or apolymer solution may be applied to base balloon 130 and/or to fibers 134to facilitate placement of fibers 134 on the base balloon, forming afiber/polymer matrix upon curing. The adhesive or polymer solution, oncecured, may be thermally-weldable to facilitate thermal bonding of thematerials. In one embodiment, the solution is a soluble nylon in asolvent such as an alcohol. As illustrated, fibers 134 may be spacedequidistant apart and substantially parallel to longitudinal axis 108and extend the length of base balloon 130. In one variation, from about15 to about 30 fibers 134 per inch having a thickness from about 0.0005to about 0.025 inch are used for balloons of 4 to 12 French.

Referring now to FIG. 7, after longitudinally oriented fibers 134 havebeen applied to base balloon 130 and any curing, if necessary, has beendone, one or more hoop fibers 142 are wound onto the base balloon. Thefibers 142 of the second fiber layer 140 may be perpendicular to orsubstantially perpendicular to longitudinally oriented fibers 134 offirst fiber layer 132. In one embodiment, circumferential fibers areperpendicular within about 10 to about 15 degrees of longitudinallyoriented fibers 134. This transverse placement of hoop fibers 142relative to longitudinal fibers 132 provides for radial stability of thefiber-reinforced balloon 100. Mandrel 400 or 500 may be pressurizedduring the process to retain the desired shape as hoop fibers 142 areapplied over the first fiber layer.

Referring still to FIG. 7, hoop fibers 142 having a thickness of about0.0005 to 0.025 inch may be wound over first fiber layer 132 at a rateof from about 30 to 80 wraps per inch in a generally parallel series ofcircumferential continuous loops to form second fiber layer 140. Inanother embodiment, hoop fibers 142 are wound over first fiber layer 132at a rate of from 40 to about 60 wraps per inch in a substantiallyparallel series of circumferential continuous loops wherein the fiber issubstantially perpendicular to the longitudinal axis of the balloon. Inone variation, semi-elastic fibers hoop fibers 142 are wrappedcircumferentially around the balloon from one neck wall to the oppositeneck wall substantially transverse to the longitudinal axis of theballoon. In another embodiment, hoop fibers 142 are wrappedcircumferentially around the balloon from one cone wall to the oppositecone wall.

In one embodiment, a ribbon shaped semi-elastic fiber 142 having a widthof approximately 0.020 inches is wound at a rate of approximately 50fibers per inch. An adhesive such as a urethane or a polymer solution,for example a soluble nylon in alcohol, may be applied to base balloon130 to provide a “tacky” surface to facilitate placement of hoop fibers142 on the base balloon. The soluble nylon will be incorporated into afiber/polymer matrix upon curing. The adhesive or polymer solution, oncecured, may be thermally-weldable to facilitate subsequent thermalprocessing and bonding of the layers together.

Turning to FIG. 8 after second fiber layer 140 has been formed and anynecessary curing has been done, an outer layer 144 may be applied oversecond fiber layer 140. Outer layer 144 may be applied as a film or atape 800 wrapped over second fiber layer 140. An adhesive such as aurethane or a compatible polymer solution may be applied over secondfiber layer or tape 800 to facilitate placement of outer layer 144. Inone embodiment, the material of outer layer 144 is the same or amaterial similar to that used to form base balloon 130 so as to closelymatch the physical properties of the underlying materials. The materialof outer layer 144 may be selected to be thermally or chemicallyweldable to the material of base balloon 130 to facilitate bonding ofthe layers. In other embodiments, outer layer 144 may be formed from apolymer solution applied by spraying, brushing or dipping the solutionover second fiber layer 140.

In one embodiment, after outer layer 144 has been applied over secondfiber layer 140 and allowed to cure, if necessary, mandrel 400 or 500may be removed from balloon. In another embodiment, mandrel 400 or 500with the base balloon 130, first and second fiber layers 132, 140 andouter layer 144 is placed into a die for heating. In some embodiments,mandrel 400 or 500 may be pressurized to conform the mandrel to theinterior walls of the die. The die is then heated from about 300° F. toabout 350° F. for a period from about 30 seconds to about 90 seconds tothermally weld one or more of the base balloon 130, first and secondfiber layers 132, 140 and outer layer 144 together. In one embodiment,the die may be heated in an oven. Alternatively, the die may incorporateintegral heating elements. In one variation, base balloon 130, outerlayer 144 and any intervening layers or coatings are thermally weldedtogether to encapsulate fibers 134 and 142 in a continuous polymermatrix.

Turning to FIG. 9, in an alternative embodiment, a first fiber layer 132(FIG. 2) layer may be formed from a patterned sheet 900 of woven,non-woven, knitted or braided material formed from semi-elastic fibers.Patterned sheet 900 may be made as described in co-pending U.S.application Ser. No. 12/187,259, filed Aug. 6, 2008 for a “Non-CompliantMedical Balloon” except that sheet 900 may be formed from semi-elasticfibers rather than substantially inelastic fibers.

FIG. 10 illustrates a woven material 1000 wherein fibers or filaments1002 are interlaced. Fibers 1002 may be flattened prior to weaving asdescribed above, or the woven material 1000 may be pressed, for examplebetween rollers to achieve the desired thickness. In one variation,woven material 1000 may be coated with a thermally-weldable polymer,clamped between plates and heated to embed the fibers 1002 within thethermally-weldable polymer to produce a sheet having smooth surfaces.Alternatively, a film formed from a thermally-weldable polymer materialmay be placed over woven material 1000 and heated to encapsulate fibers1002 in a polymer matrix.

As illustrated, the weave of material 1000 is shown with a highporosity, i.e., a relatively large amount of open space between fibers1002. Other woven fabrics having greater or lesser porosities, includingthose having a very tight weave with essentially no porosity may be usedin other embodiments. After fibers 1002 have been encapsulated into thewall of the balloon the angles (denoted “A”) between the fiberspreferentially remain constant when a balloon incorporating material1000 is inflated and deflated.

FIG. 11 illustrates a braided material 1100 formed from semi-elasticfibers 1102. Braided material 1100 employs a fiber configuration inwhich three or more fibers are intertwined in such a way that no twofibers are twisted exclusively around one another. Braided material 1100is formed from fibers 1102 that may be flattened before braiding.Alternatively, braided material 1100 may be otherwise processed toachieve the desired thickness. Braided material 1100 may be coated witha thermally-weldable polymer material and heated to embed fibers 1102within a polymer matrix to produce sheet having uniform smooth surfaces.After material 1100 is incorporated into the wall of a balloon, such asmedical balloon 100 of FIG. 1, fibers 1102 are encapsulated into thewall of the balloon such that the angles (denoted “A”) between thefibers preferentially remain constant when a balloon incorporatingmaterial 1100 is inflated and deflated.

FIGS. 12 and 13 illustrate a semi-elastic knitted material 1200 and asemi-elastic non-woven material 1300, respectively. Knitted material1200 is produced by intertwining fibers 1202 in a series ofinterconnected loops 1204 rather than by weaving. In this fashion, loops1204 of fibers 1202 are mechanically interlocked. A weft-knittedstructure consists of horizontal, parallel courses of fibers andrequires only a single fiber 1202. Alternatively, warp knitting requiresone fiber 1202 for every stitch in the course, or horizontal row; thesefibers make vertical parallel walls. In contrast, non-woven material1300 are typically made from randomly-oriented fibers that are neitherwoven nor knitted. Fibers 1302 in non-woven fabrics typically have a webstructure in which small fibers or filaments are held together byinter-fiber friction (e.g., matting), thermal binding (e.g., with ameltable binder) or chemical adhesion.

Knitted material 1200 or non-woven material 1300 may be embedded in athermally-weldable polymer. In the case of the non-woven material 1300,the fibers 1302 may be randomly oriented, chopped fibers of the same orvarying lengths that form random angles (denoted “A”) at each fiberintersection. After the knitted material 1200 or non-woven material 1300fibers 1200 and 1302 are incorporated into the wall of a medical balloonsuch as balloon 100 of FIG. 1, the fibers are embedded in a polymermatrix wherein the relative positions of the loops 1204 or angles(denoted “A”) between fibers 1202 and 1302 preferably remains constantwhen a balloon incorporating materials 1200 and 1300 is inflated anddeflated.

Referring again to FIG. 9, a patterned sheet 900 of knitted, braided,woven or non-woven material is wound around mandrel 500 over baseballoon 130 as indicated by arrow 902 to form first fiber layer 132(FIGS. 2 and 3). A layer or coating of an adhesive or thermally weldablepolymer may be applied to base balloon 130 before winding patternedsheet 900 around the mandrel to facilitate placement of the sheet. Inother embodiments, layers of knitted, braided, woven, non-wovenpatterned fiber sheets may be overlapped to provide multiple fiberlayers. In yet other embodiments, base balloon 130 may be omittedwherein patterned sheet 900 is applied directly to mandrel 500 afterwhich a second fiber layer and/or outer coating may be applied over thesheet.

After patterned sheet 900 has been positioned over base balloon 130,circumferential fibers may be wound around mandrel 500 over sheet 900 asillustrated in FIG. 7 to form second fiber layer 140. A layer or coatingof an adhesive or thermally weldable polymer may be applied overpatterned sheet 900 by means of spraying, brushing or dipping beforecircumferential fibers 142 are wound around the mandrel over the sheetto facilitate placement of the fiber or fibers. In other embodiments,second fiber layer 140 may be omitted. In still other embodiments,second fiber layer may be formed from a second patterned knit, woven,non-woven or braided material placed over sheet 900 on mandrel 500.After a second or subsequent fiber layer is formed, an outer layer 144of polymeric material may be formed as described in connection with FIG.8.

FIG. 14 illustrates expansion curves for various 7 millimeter medicalballoons as the balloons inflate from 4 atmospheres to the balloon'srespective rated burst pressures. Line 1402 represents a conventionalnon-reinforced nylon balloon having a rated burst pressure of 14atmospheres, Line 1404 represents a semi-compliant fiber-reinforceballoon according to the disclosure of the present application. Line1406 illustrates the expansion a conventional, non-reinforced PETballoon having a rated burst pressure of 20 atmospheres. Line 1408represents the expansion of a non-compliant, fiber-reinforced PETballoon having a rated burst pressure of 30 atmospheres.

As illustrated, line 1402 indicates that the conventional nylon balloonhas a compliance of 0.71% expansion/per atmosphere after the balloonreaches its nominal diameter and continues to be pressurized to itsrated burst pressure. However, the rated burst pressure of the balloonis only 14 atmospheres. Alternatively, the conventional non-compliantPET balloon and the non-compliant fiber-reinforced PET balloon havecompliances of 0.41% expansion/per atmosphere and 0.16% expansion/peratmosphere. In contrast, semi-compliant fiber-reinforce balloon has acompliance of 0.65% expansion/per atmosphere and a burst pressure of 20atmospheres. Thus, a semi-compliant balloon as described herein providesa moderate degree of expansion from the balloon's nominal dimensionswith the rated burst pressure of a conventional non-compliant PETballoon.

Turning to FIG. 15 a medical balloon 1500 may be formed usinglongitudinally extending, substantially non-elastic fibers 1502 andsubstantially non-elastic hoop fibers 1504. Fibers 1502 and 1504 areencapsulated between a base balloon 1506 and an outer layer or coating1508 formed from semi-elastic materials such as nylon and/or PEBAX®brand PEBA. Base balloon 1506 and outer layer 1508 may be formed aspreviously described. Referring to FIG. 15A, hoop fibers 1504 areloosely applied to a base balloon 1506 in a manner such that the fibersform a plurality of curves or “S-bends” 1510 around the circumference ofballoon 1500 in the finished balloon. Alternatively, longitudinal fibers1502 have been applied to the balloon relatively straight and in aconfiguration wherein the longitudinal fibers will be taut when theballoon reaches its fully inflated state.

When balloon 1500 is inflated, hoop fibers 1504 gradually straightenallowing balloon 1500 to expand radially as indicated by arrow 1512while longitudinally extending fibers 1502 restrain expansion of theballoon in a longitudinal direction. When substantially inelastic hoopfibers 1504 straighten and become taut as illustrated in FIG. 15B, thehoop fibers constrain further radial expansion of balloon 1500.

Turning to FIG. 16, in one embodiment, a medical balloon 1600 may beconstructed with loosely applied looped or slack substantially inelasticlongitudinal fibers 1604 and straight, relatively taught substantiallyinelastic hoop fibers 1602. In this variation, substantially inelastichoop fibers 1604 constrain further radial expansion of balloon 1600after the balloon reaches a fully inflated state, while looped or slacklongitudinal fibers 1604 permit moderate additional expansion as theballoon is further pressurized, until the longitudinal fibers becometaut.

Referring to FIG. 17, in yet another embodiment, a balloon 1700 may beconstructed with substantially inelastic longitudinal fibers 1704 andsubstantially inelastic hoop fibers 1702. As illustrated, fibers 1702and 1704 are loosely applied to a base balloon 1706 and encapsulatedbetween the balloon and an outer layer 1708. As balloon 1700 is inflatedbeyond a fully inflated state, substantially inelastic fibers 1702 and1704 become taut, constraining further expansion of the balloon in theradial and longitudinal directions.

It will be appreciated by those skilled in the art having the benefit ofthis disclosure that this semi-compliant medical balloon provides asemi-compliant medical balloon having an expansion rate of from about0.5% expansion/per atmosphere and 1.0% expansion/per atmosphere whenpressurized beyond the pressure it reaches its nominal diameter to theballoon's rated burst pressure. It should be understood that thedrawings and detailed description herein are to be regarded in anillustrative rather than a restrictive manner, and are not intended tobe limiting to the particular forms and examples disclosed. On thecontrary, included are any further modifications, changes,rearrangements, substitutions, alternatives, design choices, andembodiments apparent to those of ordinary skill in the art, withoutdeparting from the spirit and scope hereof, as defined by the followingclaims. Thus, it is intended that the following claims be interpreted toembrace all such further modifications, changes, rearrangements,substitutions, alternatives, design choices, and embodiments.

What is claimed is:
 1. A semi-compliant fiber-reinforced medical balloonthat may be inflated and deflated, and when inflated exhibits a moderatechange in radial distension across a predetermined range of internalpressures, the balloon comprising: a base balloon formed from asemi-elastic polymer material having an elongation to break of fromabout 10% to about 20%; a first fiber layer disposed over the baseballoon, the fibers of the fiber layer having an elongation to break offrom about 10% to about 20%; an outer layer formed from a semi-elasticpolymer material having an elongation to break of from about 10% toabout 20%; and wherein the semi-compliant fiber-reinforced balloon has arated burst pressure of at least 15 atmospheres and exhibits acompliance in the radial direction of from 0.5% expansion per atmosphereto about 1.0% expansion per atmosphere when pressurized from a fullyinflated diameter to the rated burst pressure of the balloon.
 2. Thesemi-compliant fiber-reinforced medical balloon of claim 1 wherein thefirst fiber layer comprises a plurality of substantially semi-elasticfibers extending along a longitudinal axis of the balloon, the fibersbeing substantially equally spaced apart around a perimeter of theballoon.
 3. The semi-compliant fiber-reinforced medical balloon of claim2 wherein the fibers of the first fiber layer have a thickness fromabout 0.0005 to about 0.025 inch and width-to-thickness ratio in therange from about 25:1 to about 45:1.
 4. The semi-compliantfiber-reinforced medical balloon of claim 2 further comprising a secondfiber layer disposed over the first fiber layer, the second fiber layercomprising semi-elastic fibers hoop fibers wrapped circumferentiallyaround the balloon and wherein the hoop fibers are substantiallytransverse to the longitudinal axis of the balloon.
 5. Thesemi-compliant fiber-reinforced medical balloon of claim 1 wherein thefirst fiber layer comprises one of a woven, knitted, non-woven orbraided fiber material.
 6. The semi-compliant fiber-reinforced medicalballoon of claim 5 further comprising a second fiber layer disposed overthe first fiber layer, the second fiber layer comprising semi-elasticfibers hoop fibers wrapped circumferentially around the balloon andwherein the hoop fibers are substantially transverse to the longitudinalaxis of the balloon.
 7. The semi-compliant medical balloon of claim 5further comprising a second fiber layer disposed over the first fiberlayer, the second fiber layer comprising one of a woven, knitted,non-woven or braided fiber material.
 8. A fiber-reinforced medicalballoon that may be inflated and deflated, the balloon comprising: afirst fiber layer, the fibers of the first fiber layer beingsubstantially inelastic and extending along a longitudinal axis of theballoon, the fibers of the first fiber layer being substantially equallyspaced apart around a circumference of the balloon; a second fiber layerdisposed over the first fiber layer, the fibers of the second fiberlayer being semi-elastic and having an elongation to break of from about10% to about 20%; an outer layer formed from a semi-elastic polymermaterial having an elongation to break of from about 10% to about 20%;and wherein the balloon has a rated burst pressure of at least 15atmospheres and exhibits a compliance of from 0.5% expansion peratmosphere to about 1.0% expansion per atmosphere in a radial directionwhen pressurized from a fully inflated diameter to the rated burstpressure of the balloon.
 9. The fiber-reinforced medical balloon ofclaim 8 wherein the second fiber layer comprises semi-elastic hoopfibers wrapped circumferentially around the and wherein the hoop fibersare substantially transverse to the longitudinal axis of the balloon.10. The fiber-reinforced medical balloon of claim 8, wherein the secondfiber layer comprises semi-elastic hoop fibers wrapped circumferentiallyaround the balloon and wherein the hoop fibers are substantiallytransverse to the longitudinal axis of the balloon.
 11. Thefiber-reinforced medical balloon of claim 8 wherein the fibers of thefirst fiber layer and second fiber layer have a thickness from about0.0005 to about 0.025 inch and width-to-thickness ratio in the rangefrom about 25:1 to about 45:1.
 12. The semi-compliant fiber-reinforcedmedical balloon of claim 8 wherein the second fiber layer comprises oneof a woven, knitted, non-woven or braided fiber material.
 13. Thefiber-reinforced medical balloon of claim 8 wherein the fibers of thefirst and second fiber layers are encapsulated in a continuous polymermatrix.
 14. The fiber-reinforced medical balloon of claim 8 wherein theballoon has a folded wall thickness of from about 0.0010 to about 0.0060inches.
 15. A fiber-reinforced semi-compliant medical balloon that maybe inflated and deflated, the balloon comprising: at least one fiberlayer, the fibers of the fiber layer being semi-elastic and having anelongation to break of from about 10% to about 20% and wherein thefibers of the fiber layer are encapsulated in a continuous polymermatrix such that the angles between the fibers do not change as theballoon is inflated and deflated; an outer layer formed from asemi-elastic polymer material having an elongation to break of fromabout 10% to about 20%; and wherein the balloon has a rated burstpressure of at least 15 atmospheres and exhibits a compliance of from0.5% expansion per atmosphere to about 1.0% expansion per atmosphere ina radial direction when pressurized from a fully inflated diameter tothe rated burst pressure of the balloon.
 16. The semi-compliantfiber-reinforced medical balloon of claim 15 further comprising firstand second fiber layers, the fibers of the first fiber layer along alongitudinal axis of the balloon, the fibers of the first fiber layerbeing substantially equally spaced apart around a circumference of theballoon, the fibers of the second fiber layer comprising semi-elasticfibers hoop fibers wrapped circumferentially around the balloon andwherein the hoop fibers are substantially transverse to the longitudinalaxis of the balloon.
 17. The semi-compliant fiber-reinforced medicalballoon of claim 15 further comprising first and second fiber layers,wherein the first fiber layer is one of a one of a woven, knitted,non-woven or braided fiber material and wherein the second fiber layercomprises semi-elastic fibers hoop fibers wrapped circumferentiallyaround the balloon and wherein the hoop fibers are substantiallytransverse to the longitudinal axis of the balloon.
 18. Thesemi-compliant fiber-reinforced medical balloon of claim 17 wherein thefibers of the second fiber layer have an elongation to break of fromabout 10% to about 20%.
 19. The semi-compliant fiber-reinforced medicalballoon of claim 17 wherein the fibers of the first and second fiberlayers are encapsulated in a continuous polymer matrix.
 20. Thesemi-compliant fiber-reinforced medical balloon of claim 17 wherein thefibers of the first and second fiber layers have a thickness from about0.0005 to about 0.025 inch and width-to-thickness ratio in the rangefrom about 25:1 to about 45:1.